1. Field of the Invention
The present invention relates to a part mounting apparatus, and more particularly, to a head assembly for a part mounting apparatus having a plurality of spindle units, and a part mounting apparatus adopting the same.
2. Description of the Related Art
Part mounting apparatuses having a fast and accurate mounting function have been developed in response to the needs of high integration, high functions and being small and light weight of various electronic devices. The performance of the part mounting apparatus is determined by various factors, in particular, by how a head where an absorbing nozzle is installed for absorbing parts can be rapidly and accurately moved and located at a predetermined position. To rapidly and accurately position the head at a desired position, the size and weight of the head needs to be decreased. Also, to accurately grab a part, many methods and apparatuses have been developed.
Typically, a head performs a vertical elevation movement and a rotation movement. For these two movements, a timing belt, gear or ball screw is used as a power transfer mechanism. That is, in a conventional part mounting apparatus, a spindle installed at a head is elevated up and down and rotated to mount parts on a printed circuit board. Here, the power of a motor is transferred to the spindle through a power transfer means such as a timing belt, gear or ball screw so that parts are mounted.
However, in a typical part mounting apparatus having the above power transfer mechanism, the power generated from a driving shaft of a motor is not accurately transferred to a spindle due to sagging of the timing belt or backlash of the gear. Thus, accuracy of part mounting cannot be expected. In particular, the tension of the timing belt changes according to changes in temperature so that the rotation force of the motor cannot be accurately transferred to the spindle performing elevating and rotation movements. Also, thermal and mechanical durability of the belt itself cannot be guaranteed. Also, the structure of the head becomes complicated and the weight thereof increases so that fast and accurate position selection of the head is difficult and also repair and maintenance of the apparatus is difficult.